is to assist user devices to discover access networks in their vicinity and to provide rules (policies) to prioritize and manage connections to all networks. ATSSS 3GPP has started to standardize the Access Traffic Steering, Switching & Splitting (ATSSS) function to enable 5G devices to use different types of access networks, including Wi-Fi. The ATSSS service leverages the Multipath TCP protocol to enable 5G devices to simultaneously utilize different access networks. Experience with the utilisation of Multipath TCP on iPhones has shown that the ability to simultanesouly use Wi-Fi and cellular was key to provide support seamless handovers. The first version of the ATSSS specification leverages the 0-rtt convert protocol developed within the IETF. A prototype implementation of this service has been demonstrated in August 2019. Operating system connection manager Many operating systems provide a connection manager that can automatically switch to Wi-Fi network if the connection manager detects a known Wi-Fi network. Such functionality can be found from most modern operating systems (for example from all Windows versions beginning from XP SP3, Ubuntu, Nokia N900, Android and Apple iPhone). The connection managers use various heuristics to detect the best performing network connections. These include performing DNS requests for known names over the newly activated network interfaces, sending queries to specific servers, ... When both the Wi-Fi and the cellular interfaces are activate, Android smartphones will usually prefer the Wi-Fi one since it is usually unmetered. When such a smartphone decides to switch from one interface to another, all the active TCP connections need to be reestablished. Multipath TCP solves this handover problem in a clean way. With Multipath TCP, TCP connections can use both the Wi-Fi interface and the cellular one during the handover. This means that ongoing TCP connections are not stopped when the smartphone decides to switch from one network to another. As of January 2020, Multipath TCP is natively supported on iPhones, but less frequently used on Android smartphones except in South Korea. On iPhones since iOS9, the Wi-Fi Assist subsystem monitors the quality of the underlying network connection. If the quality drops below a given threshold, Wi-Fi Assist may decide to move established Multipath TCP connections to another interface. Initially, this feature was used for the Siri application. Since iOS12, any [Multipath TCP] enabled application can benefit from this feature. Since iOS13, Apple Maps and Apple Music can also be offloaded from Wi-Fi to cellular